1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a method of monitoring calls in an Internet Protocol (IP)-based network.
2. Description of Related Art
In existing circuit-switched telecommunications networks such as the Public Switched Telephone Network (PSTN) and the legacy Public Land Mobile Network (PLMN), law enforcement agencies are able to easily monitor telephone calls because the calls, once established, are routed over a dedicated path from one subscriber to another. In an IP-based telecommunications network, this is not the case.
For IP calls that originate in a circuit-switched network, a gateway provides an interface between the circuit-switched network and the packet-switched IP network. The gateway takes bits of digitized voice, packetizes them, puts on a header, and ships them over the EP network. The packetized call may enter the core IP network at any access (edge) router near the originating subscriber. Thereafter, the individual packets follow any available route to the destination address. At that point, all of the packets exit the core network through a single access router near the destination subscriber. The same principle applies if both the calling terminal and the called terminal are IP-based. Since one or both of the subscribers involved in the call may be mobile, calls between the same subscribers may enter and leave the IP network through different access routers at different times. As a result of the changing access routers and the independent routing of the packets in the IP network, law enforcement L, agencies are not able to monitor real-time IP applications such as Voiceover-IP (VoIP) calls.
It would be advantageous to have a method of monitoring calls in an Internet Protocol (IP)-based network. The present invention provides such a method.